<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      padding: 0;
      margin: 0;
      box-sizing: border-box;
    }

    .kan {
      background-color: green;
      margin: 10px 0;
    }

    ul {
      margin-top: 100px;
      list-style: none;
      width: 50%;
    }
  </style>
</head>

<body>
  <div id="app">
    <ul>
      <li v-for="(items,index) in arrs" :key="arrs.id">
        <span v-if="index == 0" :class="cls">{{items}}</span>
        <span v-else>{{items}}</span>
      </li>
    </ul>
  </div>
</body>
<script src="../js/vue.js"></script>
<script>
  const vm = new Vue({
    el: "#app",
    data: {
      arrs: ["好人", "坏人", "不死人", "看人", "大人", "杀人"],
      cls: "kan"
    },
    methods: {}
  });
</script>

</html>